Magnetic studies of ultrafine CoFe2O4 nanoparticles with different molecular surface coatings.

Surface functionalized ultrafine CoFe2O4 nanoparticles (NPs), with mean diameter ∼5 nm, were investigated by means of DC magnetization and AC susceptibility over the temperature range of 4-400 K. All NPs present the same CoFe2O4 core, with different molecular surface coatings, increasing gradually the number of carbon atoms in the coating layer: glycine (C2H5NO2), alanine (C3H7NO2), aminobutanoic acid (C4H9NO2), aminohexanoic acid (C6H13NO2), and aminododecanoic acid (C12H25NO2). Samples were intentionally fabricated in order to modulate the core-core magnetic dipolar interaction, as the thickness of the coating layer increases with the number of carbon atoms in the coating molecule. The magnetic data of the uncoated CoFe2O4 NPs were also collected for comparison. All investigated CoFe2O4 NPs (coated and uncoated) are in a magnetically blocked state at room temperature as evidenced by ZFC/FC measurements and the presence of hysteresis with ∼700 Oe coercivity. Low temperature magnetization scans show slightly constricted hysteresis loops with coercivity decreasing systematically with a decreasing number of carbon atoms in the coating molecule, possibly resulting from differences in magnetic dipole coupling between NPs. Large thermomagnetic irreversibility, slow monotonic increase in the FC magnetization and non-saturation of the magnetization give evidence for the cluster glass (CG) nature in the CoFe2O4 NPs. The out of phase part (χ'') of AC susceptibility for all samples shows a clear frequency dependent hump which was analyzed to distinguish superparamagnetic (SPM), cluster glass (CG) and spin glass (SG) behavior by using Néel-Arrhenius, Vogel-Fulcher, and power law fittings. These analyses rule out the SPM state and suggest the presence of significant inter-cluster dipolar interaction, giving rise to CG cooperative freezing in the high-temperature region. In the low-temperature range, however, the disordered spins on the nanoparticle's surface play an important role in the formation of the SG-like state, as evidenced by Arrott plots and temperature dependency of dM/dH in the initial magnetization curves. In summary, the magnetic measurements showed that undercooling the system evolves from a SPM state of weakly interacting spin clusters, through the CG state induced by strong dipolar interaction, to the SG state resulting from the frustration of the disordered surface spins.

Combination of selol nanocapsules and magnetic hyperthermia hinders breast tumor growth in aged mice after a short-time treatment.

Short time treatment with reduced dosages of selol-loaded PLGA nanocapsules (NcSel) combined with magnetic hyperthermia (MHT) is evaluated in aged Erhlich tumor-bearing mice. Clinical, hematological, biochemical, genotoxic and histopathological parameters are assessed during 7 d treatment with NcSel and MHT, separately or combined. The time evolution of the tumor volume is successfully modeled using the logistic mathematical model. The combined therapy comprising NcSel and MHT is able to hinder primary tumor growth and a case of complete tumor remission is recorded. Moreover, no metastasis was diagnosed and the adverse effects are negligible. NcSel plus MHT may represent an effective and safe alternative to cancer control in aged patients. Future clinical trials are encouraged.

Magnetic studies of polylactic-co-glicolic acid nanocapsules loaded with selol and γ-Fe2O3 nanoparticles.

The as-prepared (MSE-NCs sample) and lyophilized (LMSE-NCs sample) polylactic-co-glicolic acid (PLGA) nanocapsules loaded with maghemite (γ-Fe2O3) nanoparticles and selol (Se-based anticancer drug) were investigated by means of dc magnetization, ac susceptibility and electron spin resonance (ESR) measurements over the temperature range of 4-300 K. The magnetic data of the as-synthesized nanocapsules containing only maghemite nanoparticles (M-NCs sample) or selol (SE-NCs sample) were also collected for comparison. The magnetic nanocapsules reveal perfect superparamagnetic (SPM) behavior only around room temperature; at temperatures lower than 200 K the SPM scaling is not observed and all samples behave as interacting superparamagnetic (ISPM) materials. The evolution from the ISPM to the SPM regime is marked by a steady decrease in the hysteretic properties of all samples, with the temperature dependence of the coercivity decreasing slower than the T1/2 behavior predicted for non-interacting SPM particles. The SPM character of the samples is also confirmed by the occurrence of a maximum in the temperature dependence of both real χ'(T) and imaginary χ''(T) components of the ac magnetic susceptibility, which shifts towards higher temperatures with increasing frequency. Moreover, upon decreasing the temperature the ESR signal shifts to lower fields and gradually broadens, following closely the predictions for the ESR of SPM particles. Additionally, an unusual giant diamagnetic response is observed at low temperatures. The ZFC magnetization is found to reverse its direction and becomes diamagnetic, whereas the FC branch remains positive. Even when compared with usual superconductors, the order of the diamagnetic susceptibility for the lyophilized sample (-10-2 emu g-1 Oe-1) is quite considerable. The nanocapsules herein reported and the presented analysis of their magnetic properties we envisage can support the engineering of magnetic nanocapsules for applications in magnetic drug delivery systems and as magnetic hyperthermia inductors in antitumor therapy.

Magnetic studies of layer-by-layer assembled polyvinyl alcohol/iron oxide nanofilms.

This study reports on investigation of the magnetic properties of layer-by-layer (LbL) assembled nanofilms comprising polyvinyl alcohol (PVA) and citrate-coated magnetite (cit-MAG) nanoparticles deposited onto silicon (SF sample) and glass (GF sample) substrates. DC magnetization measurements were performed over the temperature range of 4 K to 300 K, in the applied magnetic field range of ±60 kOe. The magnetic data of the as-synthesized cit-MAG nanoparticles (F sample) are also collected for comparison. The three as-fabricated samples reveal perfect superparamagnetic (SPM) behavior only around room temperature; at temperatures lower than 200 K the SPM scaling is not observed and all samples behave as interacting superparamagnetic (ISPM) materials. The evolution from the ISPM to the SPM regime is marked by a steady decrease in the hysteretic properties of all samples, with the temperature-dependence of the coercivity decreasing slower than the T1/2 behavior predicted for non-interacting superparamagnetic particles. The modified Bloch's law used to assess information on nanoparticles' surface spins gives the Bloch's exponent close to 2 (for the F and SF samples) and close to 1 (for the GF sample). Interestingly, the surface spin freezing temperature (Tf) is 8 ± 1 K for all samples. The magnetic behavior of all three samples can be described within the model picture of a core-shell structure for the cit-MAG nanoparticles; the core comprising magnetically-ordered spins whereas the shell behaving as a spin-glass-like system. However, the contribution of the shell magnetism to the effective magnetic properties is much more evident in the GF sample in which magnetic dipole-dipole interaction is three-times weaker than in the SF sample and two times weaker than in the F sample. In contrast, the strong magnetic dipole-dipole interaction in the SF sample affects the surface spins, hindering the onset of magnetically-ordered regions in the nanoparticle's shell, making the surface magnetism contribution negligible. The LbL-fabricated nanofilms herein reported and the presented analysis of their magnetic properties we envisage can support the engineering of magnetic nanofilms for multiple applications.

Decoration of a Poly(methyl vinyl ether-co-maleic anhydride)-Shelled Selol Nanocapsule with Folic Acid Increases Its Activity Against Different Cancer Cell Lines In Vitro.

Due to the low therapeutic index of different chemotherapeutic drugs used for cancer treatment, the development of new anticancer drugs remains an intense field of research. A recently developed mixture of selenitetriacylglycerides, selol, was shown to be active against different cancer cells in vitro. As this compound is highly hydrophobic, it was encapsulated, in a previous study, into poly(methyl vinyl ether-co-maleic anhydride)-shelled nanocapsules in order to improve its dispersibility in aqueous media. Following this line of research, the present report aimed at enhancing the In Vitro activity of the selol nanocapsules against cancerous cells by decorating their surface with folic acid. It is known that several cancer cells overexpress folate receptors. Stable folic acid-decorated selol nanocapsules (SNP-FA) were obtained, which showed to be spherical, with a hydro-dynamic diameter of 364 nm, and zeta potential of -24 mV. In comparison to non-decorated selol nanocapsules, SNP-FA presented higher activity against 4T1, MCF-7 and HeLa cells. Moreover, the decoration of the nanocapsules did not alter their toxicity towards fibroblasts, NIH-3T3 cells. These results show that the decoration with folic acid increased the toxicity of selol nanocapsules to cancer cells. These nanocapsules, besides enabling to disperse selol in an aqueous medium, increased the toxicity of this drug In Vitro, and may be useful to treat cancer in vivo, potentially increasing the specificity of selol towards cancer cells.

Selol nanocapsules with a poly(methyl vinyl ether-co-maleic anhydride) shell conjugated to doxorubicin for combinatorial chemotherapy against murine breast adenocarcinoma in vivo.

Nanocapsules containing selol and doxorubicin (NCS-DOX) with an oily core of selol and a shell of poly(methyl vinyl ether-co-maleic anhydride) covalently conjugated to doxorubicin were developed in a previous work. In this study, these nanocapsules showed a similar antitumour effect in comparison to the free doxorubicin (DOX) treatment, but showed no evident DOX-related cardiotoxicity, as evidenced by serum creatine kinase-MB (CK-MB) activity. The histopathological analysis showed that the free DOX treatment induced more intense morphological damage to myocardial tissues in comparison to NCS-DOX treatment. Animals treated with free DOX presented important muscle fibre degradation and animals treated with NCS-DOX, heart tissue did not present signals of muscle fibre degeneration. These results indicate that the cardiotoxicity related to DOX is reduced when this drug is carried by the NCS-DOX. Noteworthy, biodistribution analyses showed that NCS-DOX accumulated more intensely in tumours than the free DOX. Thus, this study reinforces the importance of the development of nanocapsules as drug carriers for the treatment of cancer.

Nanocapsules for the co-delivery of selol and doxorubicin to breast adenocarcinoma 4T1 cells in vitro.

Nanocapsules (NCS-DOX) with an oily core of selol and a shell of poly(methyl vinyl ether-co-maleic anhydride) covalently conjugated to doxorubicin were developed. These nanocapsules are spherical, with an average hydrodynamic diameter of about 170 nm, and with negative zeta potential. NCS-DOX effectively co-delivered the selol and the doxorubicin into 4T1 cells and changed the intracellular distribution of DOX from the nuclei to the mitochondria. Moreover, a significantly increased cytotoxicity against 4T1 cells was observed, which is suggestive of additive or synergic effect of selol and doxorubicin. In conclusion, PVM/MA nanocapsules are suitable platforms to co-deliver drugs into cancer cells.

Antitumor activity and systemic effects of PVM/MA-shelled selol nanocapsules in lung adenocarcinoma-bearing mice.

Selol is a semi-synthetic compound containing selenite that is effective against cancerous cells and safer for clinical applications in comparison with other inorganic forms of selenite. Recently, we have developed a formulation of poly(methyl vinyl ether-co-maleic anhydride)-shelled selol nanocapsules (SPN), which reduced the proliferative activity of lung adenocarcinoma cells and presented little deleterious effects on normal cells in in vitro studies. In this study, we report on the antitumor activity and systemic effects induced by this formulation in chemically induced lung adenocarcinoma-bearing mice. The in vivo antitumor activity of the SPN was verified by macroscopic quantification, immunohistochemistry and morphological analyses. Toxicity analyses were performed by evaluations of the kidney, liver, and spleen; analyses of hemogram and plasma levels of alanine aminotransferase, aspartate transaminase, urea, and creatinine; and DNA fragmentation and cell cycle activity of the bone marrow cells. Furthermore, we investigated the potential of the SPN formulation to cause hemolysis, activate the complement system, provoke an inflammatory response and change the conformation of the plasma proteins. Our results showed that the SPN reduced the area of the surface tumor nodules but not the total number of tumor nodules. The biochemical and hematological findings were suggestive of the low systemic toxicity of the SPN formulation. The surface properties of the selol nanocapsules point to characteristics that are consistent with the treatment of the tumors in vivo: low hemolytic activity, weak inflammatory reaction with no activation of the complement system, and mild or absent conformational changes of the plasma proteins. In conclusion, this report suggests that the SPN formulation investigated herein exhibits anti-tumoral effects against lung adenocarcinoma in vivo and is associated with low systemic toxicity and high biocompatibility.

PVM/MA-shelled selol nanocapsules promote cell cycle arrest in A549 lung adenocarcinoma cells.

BACKGROUND: Selol is an oily mixture of selenitetriacylglycerides that was obtained as a semi-synthetic compound containing selenite. Selol is effective against cancerous cells and less toxic to normal cells compared with inorganic forms of selenite. However, Selol's hydrophobicity hinders its administration in vivo. Therefore, the present study aimed to produce a formulation of Selol nanocapsules (SPN) and to test its effectiveness against pulmonary adenocarcinoma cells (A549). RESULTS: Nanocapsules were produced through an interfacial nanoprecipitation method. The polymer shell was composed of poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA) copolymer. The obtained nanocapsules were monodisperse and stable. Both free Selol (S) and SPN reduced the viability of A549 cells, whereas S induced a greater reduction in non-tumor cell viability than SPN. The suppressor effect of SPN was primarily associated to the G2/M arrest of the cell cycle, as was corroborated by the down-regulations of the CCNB1 and CDC25C genes. Apoptosis and necrosis were induced by Selol in a discrete percentage of A549 cells. SPN also increased the production of reactive oxygen species, leading to oxidative cellular damage and to the overexpression of the GPX1, CYP1A1, BAX and BCL2 genes. CONCLUSIONS: This study presents a stable formulation of PVM/MA-shelled Selol nanocapsules and provides the first demonstration that Selol promotes G2/M arrest in cancerous cells.

Co-nanoencapsulation of magnetic nanoparticles and selol for breast tumor treatment: in vitro evaluation of cytotoxicity and magnetohyperthermia efficacy.

Antitumor activities have been described in selol, a hydrophobic mixture of molecules containing selenium in their structure, and also in maghemite magnetic nanoparticles (MNPs). Both selol and MNPs were co-encapsulated within poly(lactic-co-glycolic acid) (PLGA) nanocapsules for therapeutic purposes. The PLGA-nanocapsules loaded with MNPs and selol were labeled MSE-NC and characterized by transmission and scanning electron microscopy, electrophoretic mobility, photon correlation spectroscopy, presenting a monodisperse profile, and positive charge. The antitumor effect of MSE-NC was evaluated using normal (MCF-10A) and neoplastic (4T1 and MCF-7) breast cell lines. Nanocapsules containing only MNPs or selol were used as control. MTT assay showed that the cytotoxicity induced by MSE-NC was dose and time dependent. Normal cells were less affected than tumor cells. Cell death occurred mainly by apoptosis. Further exposure of MSE-NC treated neoplastic breast cells to an alternating magnetic field increased the antitumor effect of MSE-NC. It was concluded that selol-loaded magnetic PLGA-nanocapsules (MSE-NC) represent an effective magnetic material platform to promote magnetohyperthermia and thus a potential system for antitumor therapy.

Magnetic studies of ferrofluid-modified microbial cells.

Microbial cells (Kluyveromyces fragilis and Chlorella vulgaris) efficiently interacted with maghemite nanoparticles stabilized as low-pH ionic magnetic fluid, leading to the formation of magnetically labeled cells. This simple procedure allows to use the prepared materials as new cheap and easy to get magnetic affinity adsorbents to the removal of water-soluble dyes from polluted water sources using magnetic separation techniques. Magnetically modified cells were investigated by means of electron spin resonance spectroscopy and conventional magnetic methods over the temperature range 4-300 K. The magnetic behavior of these materials was dominated by the superparamagnetic relaxation of isolated single domain maghemite particles although a little amount of agglomerates was also present on the cell surface. However, these agglomerates were sufficiently small to show at static conditions the superparamagnetic behavior at room temperature. Therefore, the ferrofluid-modified microbial cells represent new interesting magnetic affinity adsorbents which could be applied for large-scale magnetic separation processes.